1. Field of Invention
This invention relates to color reproduction.
2. Description of Related Art
Generally, documents, including color documents, can be transmitted and received over a network. Furthermore, color documents can be sent to and output by a networked color image forming device, such as, for example, a color printer.
Additionally, if a color document is outputted on two different color image forming devices, the two outputted color documents, when compared side-by-side, can show variations in color tone, saturation, and hue. The level of variation can be slight, and barely noticeable, or the level of variation can be extreme and very noticeable. Furthermore, if either of the two outputted color documents is compared to an image of the color document displayed on a color display monitor of, for example, a computer, variations will be noticeable between the printed color document and the displayed color document.
Color matching techniques, or color matching, match the color characteristics of one color device to the color characteristics of another color device. Color matching is generally used when color images are transferred between different color devices, such as, for example, between color display monitors, color scanners, or color marking devices. Color matching is necessary because different color devices usually describe color in different terms, usually operate in different color spaces, and usually have different color capabilities.
For example, most color display monitors, such as, for example, color computer monitors, display colors in the red/green/blue (RGB) color space, i.e., with respect to the amount of red, green, and blue that a particular displayed color contains. Using this technique, the color yellow, for example, is displayed on a color display monitor by combining a red image value of 255 red with a green image value of 255 green and a blue image value of zero.
Furthermore, the red, green, and blue (RGB) color values associated with the particular colors for a color display monitor are device dependent. This means that the RGB values associated with a particular color, viewed on a specific color display monitor, are unique to that specific color display monitor or, at least, to that brand of color display monitor. Simply put, because RGB color values are device dependent, if identical RGB color values, such as, for example, a red image value of 255 red, a green image value of 255 green, and a blue image value of zero, are input and displayed on two different color display monitors, the resulting yellow color displayed on the two color display monitors will probably not appear exactly alike.
Similarly, most color image forming devices output colors in device dependent terms. However, unlike most color display monitors, most color marking devices use a cyan, magenta, yellow, and black (CMYK) color space, i.e., a combination of cyan, magenta, yellow and black (CMYK) to arrive at the color marking device""s outputted colors. Consequently, as with RGB color values, CMYK color values are device dependent as well. Thus, as described above with respect to colors being displayed on color display monitors, if identical CMYK colors are printed on two different color marking devices, the outputted colors will probably not appear exactly alike.
To add to the complexity of color matching between color image forming devices, different color image forming devices can use different types of toners, dyes, pigments, or inks to produce the outputted color images. Likewise, the color images can be produced on a wide range of copy media. Images can be produced, for example, on copy media ranging from paper to plastic, from fabric to metal. In each case, each combination of colorant and media produces a different optical appearance.
Moreover, different color devices have different color capabilities. Every color device, whether it is a color scanner, a color marking device, or a color display monitor, has a color gamut, i.e., a range of colors that it can capture, produce, or display. To illustrate the problems encountered when color matching is attempted between two different devices having two different color gamuts, consider color display monitors and color marking devices. Most color display monitors can display hundreds of thousands of colors. Conversely, color marking devices usually have a significantly smaller number of producable colors. Therefore, the gamut of a color display monitor usually exceeds the gamut of a color marking device. Thus, some of the colors that can be displayed on a color display monitor cannot be produced by a color marking device.
In an attempt to solve the problem of color matching, various color matching techniques have been developed that use models to translate colors from one color space to another color space. These models usually manifest themselves in the form of predetermined multi-dimensional look-up tables. These predetermined multi-dimensional look-up tables translate colors from one color space to another color space while attempting to maintain the translated color""s perceived appearance. For example, if a user creates an image on a color display monitor and subsequently outputs the created image without any color matching, the colors observed on the outputted image may differ significantly from the colors originally observed on the color display monitor. However, if some type of color matching model is used, the discrepancies between the originally observed colors on the color display monitor and the colors observed on the outputted image can be reduced.
One method of creating and updating a multi-dimensional look-up table is to is provide a color sensor inside each color marking device. This embedded color sensor is used to measure the color characteristics of the color marking device by measuring the color characteristics of an outputted color patch pattern. Feed-back information about the color characteristics of the outputted color patch pattern is then provided to the color marking device to improve further color reproduction. For example, U.S. patent application Ser. No. 09/083,203, incorporated herein by reference in its entirety, discloses a method of reducing and controlling color drift between a desired image and an output image printed by a marking device that is intended to match the desired image. In the 203 application a current output color in the output image is detected with a color sensing device. A difference between the current output color in the output image and a corresponding color in the desired image is then determined. A next output color in the output image is automatically set equal to a corrected color that minimizes the difference between the next output color and the corresponding color in an output image. Preferably, this is done on a real-time basis.
Additionally, in U.S. patent application Ser. No. 09/083,202, incorporated herein by reference in its entirety, the error in an output color of a colored output image in a marking device intended to match a desired image is reduced. In the 202 application, a current output color in the output image is detected with a color sensing device. A difference between the current output color and a corresponding target color under standard conditions is determined. A marking device input-output relationship for a next output color is automatically set based on the difference between the current output color and the corresponding target color under standard conditions to minimize the difference between the next output color and the corresponding target color.
Furthermore, in U.S. patent application Ser. No. 09/083,114, incorporated herein by reference in its entirety, colorants are mixed to achieve a target color by combining individual colorants, detecting an output color of the combined colorants with a color sensing device and automatically adjusting the output color based on comparison between the detected output color and the target color.
Using current color matching techniques, relatively close color matching can be achieved between marking devices if a properly calibrated device, such as, for example, a digital front end (DFE), is used to drive the marking devices. However, because uniformly producing correctly calibrated color documents is one of the most difficult aspects of color document services, the quality of color documents can not be guaranteed between different marking devices.
Thus, for a digital front end (DFE) to be effective, it must be either manually calibrated by a color specialist or calibrated using a color patch pattern and a color scanner, as described above. Unfortunately, allowing different color specialists to calibrate different digital front ends (DFEs) can lead to inconsistent calibration of the digital front ends (DFEs). Furthermore, even if the color patch pattern technique is used to help calibrate a color marking device, it still remains difficult to guarantee that a color marking device in another location has been properly calibrated. This inconsistent or unverifiable calibration, in turn, produces inconsistent color reproduction between marking devices. Thus, eventually, even calibrated marking devices often fail to maintain consistent color outputs.
Furthermore, once a particular marking device has been calibrated, it is difficult to determine how long the marking device will remain in calibration. Over time, the color quality of the documents printed by a previously calibrated marking device will deteriorate, or drift.
Additionally, when a marking device is calibrated, the marking device is calibrated with respect to a particular type of colorant and a particular type of copy media. Thus, each time a different type of colorant or copy media is used, the marking device must be re-calibrated. If the marking device is not re-calibrated, the marking device will function as an un-calibrated marking device.
Consequently, it is nearly impossible to guarantee that the color characteristics and quality of an outputted document, for example, downloaded from a network by two different users, and printed using two different printers, will have the same color appearance. Likewise, it is nearly impossible to guarantee that the color characteristics and quality of an outputted document, will match the color characteristics and quality of the document as it appears on a color display monitor.
This invention provides systems and methods that enable color matching or consistency between color image forming devices without requiring the intervention of either a user or a color specialists.
This invention separately provides a device independent color control (DICC) server that provides spectral or colorimetric matching of images printed on different color marking devices. This invention separately provides device independent color control systems and methods that use a standalone device independent color control (DICC) server to provide improved color consistency between different marking devices and/or display devices. This invention separately provides device independent color control software installed on a general network server. This invention separately provides systems and methods that use a specialized hardware-independent device independent color control (DICC) printer-only server.
This invention separately provides device independent color control systems and methods that use a standalone device independent color control (DICC) server and associated devices and techniques to provide color consistency services and to improve consistent document appearance between any number of connected image forming devices and/or display devices on a distributed network.
This invention separately provides a device independent color control server that is a separate hardware/software unit.
This invention separately provides device independent color control systems and methods that analyze a color document printed by a particular color marking device, and, based on that analysis, calibrates that particular color marking device.
This invention separately provides device independent color control systems and methods that analyze a color pattern displayed by a particular color display monitor, and, based on that analysis, calibrates that particular color display monitor.
This invention separately provides device independent color control systems and methods that work over a network to service printers worldwide.
This invention separately provides device independent color control systems and methods that work over a network to service color display monitors worldwide.
This invention separately provides device independent color control systems and methods that improve globally consistent color reproduction.
This invention separately provides device independent color control systems and methods that render an xe2x80x9cexact matchxe2x80x9d or an xe2x80x9coptimal matchxe2x80x9d to color documents from the same or different image output terminals (IOT).
The color image forming devices can, for example, be color printers of similar or differing technologies. Thus, the device independent color control (DICC) server according to this invention will produce improved consistency of color outputs between separately outputted documents. Using the device independent color control (DICC) server according to this invention will result, for example, in five different color outputs of the same document having similar color characteristics, even if, for example, one copy of the color document is produced using a digital Xerox(copyright) printer, another copy is produced using a Xerographic printer, another copy is produced using a Xerox(copyright) DocuColor 40(trademark) printer, another copy is produced using a Cannon(copyright) CLC1000(trademark) printer, and yet another copy is produced using an ink jet NC20(trademark) printer.
Various exemplary embodiments of a device independent color control server according to this invention include a non-contact, high speed color sensing device in an output paper path or on the output tray of each marking device, a server, and interface hardware for communicating between the marking devices, the sensors and the server.
In various exemplary embodiments, the device independent color control server includes a high speed color sensing device on the display of each color display monitor, a server computing platform, and interface hardware for communication between the displays, the sensors and the server.
In various exemplary embodiments, the server-computing platform executes specialized color control methods. In various exemplary embodiments, the server-computing platform is a stand-alone server-computing platform. In other exemplary embodiments, the server-computing platform is embedded within each marking and/or display device.
In various exemplary embodiments, the interface hardware is a specialized network plug-in card. In various other exemplary embodiments, the interface hardware is a combination of wireless transmitters and one or more wireless receivers.
In various exemplary embodiments, the apparatuses, systems and methods of this invention function either automatically or by selection of a routine, such as, for example, a xe2x80x9ccolor warranteesxe2x80x9d routine.
These and other features and advantages of this invention are described in or are apparent from the following detailed description of various exemplary embodiments of the systems and methods of this invention.